The present invention generally relates to concentrates and to colored compositions, such as thermal compositions. More particularly, the present invention relates to color concentrates and to hot melt compositions, such as hot melt inks and thermal printing mediums. Additionally, the present invention relates to various methods of making color concentrates thermal compositions, such as color concentrates hot melt compositions, and to a method of increasing colorant concentration in thermal components and compositions.
Ink jet printers have benefitted from various technical breakthroughs to become increasingly reliable and productive. Advances in speed, response, and print definition and clarity are examples of just a few of the many advances in ink jet printers. Advances in ink technology must occur to fully reap the benefits of the improved ink jet printers. Improvements to operational and rheological characteristics of inks used in ink jet printers are envisioned. For example, ink improvements that enhance ink flow through ink jet printers are needed. Additionally, advances that enhance colorant concentrations and colorant uniformity in the inks are desirable. Improved interaction between inks and substrates the inks are applied to is also needed.
Inks typically include at least a colorant and a colorant transport vehicle. Polymeric resins generally make good transport vehicles for colorants such as pigments and dyes. Additionally, polymeric resins offer good operational properties including thermal stability. However, ink compositions that are made of polymeric resins sometimes require modification to enhance performance of the compositions during certain operations. For example, the viscosity of inks that are made of polymeric resins is typically above the viscosity range that is desirable for good ink jet printer operation.
One alternative to polymeric resins as colorant transport vehicles is wax, including wax-like materials. Waxes have a relatively low viscosity, as compared to polymeric resins. Thus, wax-based inks might be expected to improve ink jet operation. However, aside from the lower viscosity, operational properties of wax-based inks are less than desirable. For example, the wax base of the wax-based inks does not typically solubilize dyes or disperse pigments well. Also, wax-based inks do not adhere well to many substrates, such as paper, and can be relatively easily abraded from the substrates. Additionally, though waxes are somewhat transparent in the liquid state, waxes are typically highly crystalline. Therefore, wax-based inks are typically not very transparent in the solid state.
Another option for reducing ink viscosity and improving ink jet operation is to combine wax with polymeric resin in forming ink compositions. However, though waxes can be added to polymeric resins to reduce ink viscosities, dye solubility and pigment dispersibility are each limited in ink compositions that include polymeric resin and wax, as compared to ink compositions that include polymeric resin but not wax. Additionally, wax that is added to polymeric resin diminishes ink adherence to substrates such as paper. Furthermore, the scuff resistance of existing inks that include combinations of wax and polymeric resin, as well as, the jet-ability of such inks also suffer. Jetability relates to various operational considerations and characteristics, such as uniformity of flow in the liquid state, nozzle-clogging characteristics, surface tension, droplet size, and the shape of ink droplets after application to substrates.
Nonetheless, examples of ink and thermal compositions that include wax, polymeric resins, or combinations of waxes and polymeric resins do exist. For example, U.S. Pat. No. 4,390,369 to Merritt et al. discloses wax-based ink formulations for discharge at temperatures above ambient from an ink jet apparatus. Ink formulations prepared according to Merritt are said to provide good ink dot circularity that produces characters approaching and surpassing typewriter quality printing.
U.S. Pat. No. 4,500,896 to Kubo et al. concerns an image transfer-type, heat-sensitive recording medium. Kubo details a solid ink that contains a fusible substance and a coloring agent dispersed in the fusible substance. Examples of suitable fusible substances include various waxes and polymeric substances.
U.S. Pat. No. 4,603,172 to Albee et al. relates to polymer dispersion aids that are made from polymer salts of low molecular weight, copolymers of alpha-olefins and alpha, beta-ethylenically unsaturated carboxylic acid. Albee addresses use of the described compounds in dispersing finely divided inert materials and polymers and also describes a method of processing polymers to maximize material dispersion.
U.S. Pat. No. 4,636,258 to Hayashi et al. concerns an ink composition for thermal transfer printing that includes a copolymer, a colorant, wax, and suitable resins. The described ink composition is stated to be suitable for use as the ink layer of an electro-thermal transfer recording sheet.
U.S. Pat. No. 4,808,227 to Yuasa et al. describes a semi-solid ink for a heat transfer recording method. The semi-solid ink includes a heat-fusible binder, such as a combination of a wax and a naphthenic hydrocarbon, and may also incorporate a softening agent and a colorant.
U.S. Pat. No. 4,818,591 to Kitamura addresses a thermal transfer recording medium that includes an aqueous emulsion portion having a heat fusible layer and at least one aqueous emulsion colorant layer. Waxes are examples of compounds included in the heat-fusible layer. Various oils and polymeric resins are mentioned as possible components of the colorant layer.
U.S. Pat. No. 4,927,693 to Koshizuka also addresses a thermal transfer recording medium that includes a fusible colorant layer. The fusible colorant layer may include fusible materials, such as waxes, and also may contain polymeric resins.
U.S. Pat. No. 4,970,119 to Koshizuka describes a thermal transfer recording medium with a peel layer and a heat-softening layer. The peel layer may contain a wax and a polymer resin and may also contain a coloring material. The heat softening layer may also contain a wax and a polymeric resin and, optionally, may include a coloring material.
U.S. Pat. No. 5,071,502 to Hashimoto et al. discloses a heat sensitive recording material that includes a hot-melt heat-sensitive ink material. The heat-sensitive ink material comprises an amorphous polymer and a coloring material. The heat-sensitive ink material is coated on a support by solution coating or by hot melt coating.
U.S. Pat. No. 5,124,719 to Matsuzaki discloses an ink composition that includes first and second components and a coloring material. The coloring material dissolves in the second component, but does not dissolve in the first component. The first component and the second component have different melting points such that when the ink contacts recording paper, the first component permeates into the recording paper and the second component, containing all of the colorant, remains on the surface of the recording paper.
U.S. Pat. No. 5,134,033 to Umise et al. discloses a thermal transfer sheet that includes a heat-fusible ink layer. The heat-fusible ink layer includes carbon black, a vehicle, and an optional additive. The vehicle may include a wax or a mixture of a wax and another component, such as drying oil, resin, mineral oil, and derivatives of cellulose and rubber.
U.S. Pat. No. 5,141,559 to Shinozuka discloses an ink composition that includes a carrier vehicle for transporting a coloring material. The vehicle includes at least one high molecular weight alkyl amine, at least one high molecular weight fatty acid, and carnauba wax. The coloring material is a metallic complex-type solvent dye.
U.S. Pat. No. 5,151,120 to You et al. discloses an ink jet composition that includes a carrier, a driver, and a colorant. Suitable carriers include waxes, plastics, polymers and oligomers.
U.S. Pat. No. 5,182,572 to Merritt et al. discloses an ink composition that includes a vehicle and a coloring agent. The vehicle may include fatty acids and waxes, such as natural waxes, synthetic substances, resins, and meltable polymeric materials.
U.S. Pat. No. 5,196,475 to Lences discloses a pigment composition. The pigment composition may include salts of certain low molecular weight copolymers, pigment, and a first polymer. The first polymer may be polyamide, polyolefin, polyester, polycarbonate and phenolic resin.
U.S. Pat. No. 5,215,810 to Koshizuka relates to a thermal transfer recording medium that includes a plurality of heat softening colorant layers. The heat softening colorant layers contain a colorant, a thermofusible substance, and a thermoplastic substance. Examples of the thermofusible substance includes various waxes, higher fatty acids, higher alcohols, esters of higher fatty acids, amides, and higher amines. Examples of the thermoplastic resin include certain copolymers, elastomers, polymeric resins and rosin derivatives.
U.S. Pat. No. 5,221,335 to Williams et al. discloses pigmented hot melt inks that include colored pigments and a vehicle. The vehicle may include any suitable hydrocarbon polymer or wax-like material, certain fatty acids, or ketones of certain fatty acids.
U.S. Pat. No. 5,262,471 to Akao discloses a resin composition which comprises a modified polyolefin resin and carbon black and which may optionally include thermoplastic resins and polyolefin wax. The modified polyolefin resin is a polyolefin resin modified by an unsaturated carboxylic acid, or a derivative thereof.
U.S. Pat. No. 5,286,288 to Tobias discloses a hot melt ink composition that comprises an electrolyte and an electrolyte-solvating and dissociating compound selected from the group consisting of alkanolamides and polyethylene glycol. The ink may also include a viscosity reducing agent, a hardening agent, and a flexibilizing agent.